Can I use images rendered with blender for commercial use?
Short answer Yes.
Just as you own what you draw with a pencil, you own works you make with Blender(no difference).
To quote from blender.org

Your artwork
What you create with Blender is your sole property. All your artwork – images or movie files – including the .blend files and other data files Blender can write, is free for you to use as you like.
That means that Blender can be used commercially by artists, by studios to make animation films or vfx, by game artists to work on commercial games, by scientists for research, and by students in educational institutions.
Blender’s GNU GPL license guarantees you this freedom. Nobody is ever permitted to take it away, in contrast to trial or “educational” versions of commercial software that will forbid your work in commercial situations.

Meaning anything you make in Blender (images, scripts, add-ons, models, entire scenes, materials, textures, and so on) is yours, and you can do anything with it, without any legal notices at all.

A general note about Open-Source, not specific to Blender.
You don't have to get into details of each license.
Any OSI approved License assured you can do what you like with works created from OpenSource software. This is part of the Open-Source, definition as defined by the OSI,
http://opensource.org/osd
Points 5 and 6.


No Discrimination Against Persons or Groups

The license must not discriminate against any person or group of persons.

No Discrimination Against Fields of Endeavor

The license must not restrict anyone from making use of the program in a specific field of endeavor. For example, it may not restrict the program from being used in a business, or from being used for genetic research.